Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
CURRENT ASSETS:
Cash and cash equivalents	$ 50,219	$ 27,269
Accounts receivable, net	159,792	165,768
Materials and supplies	16,343	14,445
Prepaid expenses and other	15,621	13,332
Deferred income tax assets, net	19,666	19,385
Total current assets	261,641	240,199
PROPERTY AND EQUIPMENT, net	1,712,879	1,643,589
GOODWILL	159,963	160,277
INTANGIBLE ASSETS, net	227,145	230,628
DEFERRED INCOME TAX ASSETS, net	2,442	2,342
OTHER ASSETS, net	17,716	17,122
Total assets	2,381,786	2,294,157
CURRENT LIABILITIES:
Current portion of long-term debt	64,351	57,168
Accounts payable	112,095	134,081
Accrued expenses	70,497	69,097
Deferred income tax liabilities, net	0	925
Total current liabilities	246,943	261,271
LONG-TERM DEBT, less current portion	563,599	569,026
DEFERRED INCOME TAX LIABILITIES, net	307,681	285,780
DEFERRED ITEMS - grants from outside parties	208,785	198,824
OTHER LONG-TERM LIABILITIES	17,873	18,622
COMMITMENTS AND CONTINGENCIES	0	0
STOCKHOLDERS' EQUITY:
Additional paid-in capital	403,767	385,473
Retained earnings	800,273	741,669
Accumulated other comprehensive income	39,026	37,895
Treasury stock, at cost	(206,714)	(204,952)
Total stockholders' equity	1,036,905	960,634
Total liabilities and stockholders’ equity	2,381,786	2,294,157
Class A common shares [Member]
STOCKHOLDERS' EQUITY:
Common Stock	532	527
Class B common shares [Member]
STOCKHOLDERS' EQUITY:
Common Stock	$ 21	$ 22